This project involved analysis of two datasets from the Genetic Analysis Workshop 11. A set of data from the COGA study of alcoholism was analyzed using linkage and association techniques, finding evidence for possible linkage on chromosome 12 of a locus influencing monoamine oxidase activity and showing that this locus may be more important in smokers than in non- smokers. Another set of data was for an extremely complex computer simulated trait. Several methods of analysis both ignoring and attempting to adjust for an environmental risk factor were compared. It was found that major increases in power in sib-pair linkage analyses can be obtained by analyzing only persons exposed to the risk factor, if the environmental risk factor has a fairly large effect on penetrance. Two manuscripts have been submitted for publication.